1. Field of the Invention
The present invention relates to a video processing device that performs video signal processing to a digital video signal.
2. Description of the Related Art
In recent years, HDR contents that are supported by HDR (High Dynamic Range) of high luminance appear. The HDR contents are mastered by using a master monitor. The HDR contents are sent from source equipment and repeater equipment that are supported by HDR to a monitor and a projector via HDMI (registered trademark) or the like. The following content information is sent with a video signal.    (1) Type of EOTF (Electro-Optical Transfer Function)    (2) Maximum luminance of a mastering monitor    (3) Minimum luminance of the mastering monitor    (4) Maximum frame average luminance
The monitor converts the video signal into optical brightness based on information of (1) to (4). However, there are cases where dynamic range of the content exceeds dynamic range of the monitor depending on the content because dynamic range is narrower than the mastering monitor in the monitor that is sold in the market. In this case, luminance conversion is only performed based on each EOTF standard and black crush and halation occur. To reduce black crush and halation, it is necessary that the monitor uses content information and performs optimum luminance conversion based on dynamic range of the content. However, depending on the monitor, it decides processing uniquely based on type of EOTF and gradation collapse occurs depending on the content.
Patterns of dynamic range of the monitor are illustrated, and gradation collapse is described below using a graph of EOTF. With respect to breadth of dynamic range, 3 patterns of the following (a) to (c) are thought.    (a) Standard value>the master monitor>the content>the general monitor    (b) Standard value>the master monitor>the general monitor>the content    (c) Standard value>the content>the master monitor>the general monitorNormally, (a) is suitable and (a) is described as an example.
FIG. 8 is a diagram illustrating standard value of dynamic range. FIG. 9 is a diagram illustrating an example of dynamic range of the master monitor. FIG. 10 is a diagram illustrating an example of range of luminance signal that is included in the content. FIG. 11 is a diagram illustrating an example of dynamic range of a general monitor. As illustrated in FIG. 8 to FIG. 11, FIG. 8 to FIG. 11 match the above mentioned (a).
The monitor that decides processing uniquely based on type of EOTF performs to apply formula of EOTF as processing example. For this reason, in outside of dynamic range of the monitor, value sticks maximum value or minimum value. Thus, it is highly possible that black crush and halation occur. FIG. 12 is a diagram illustrating case where dynamic range of monitor is 0.05-700 (cd/m2). FIG. 13 is an enlarged diagram illustrating neighborhood of black crush. As illustrated in diagrams, value sticks the minimum value and black crush occurs. Further, value sticks the maximum value and halation occurs. Herein, the value of a video signal illustrated in FIG. 8 to FIG. 13 is a value in 10 bits signal.
Invention described in JP 5914802 B converts an HDR signal into a linear signal indicating luminance value. And, the invention described in JP 5914802 B converts the converted linear signal using display characteristics information and content luminance information.
The above described gradation collapse is caused by dynamic range shortage of the monitor.